1. Field of the Invention
The present invention relates to the field of racking apparatus for supporting equipment and, more particularly, to a rack assembly for plug-in type modules which provides cooling air and mechanical isolation to the modules.
2. Background Art
Electronic equipment carried on vehicles such as ships and aircraft is frequently supported on rack assemblies which also provide cooling air and mechanical isolation from vibration and shock. Such equipment is typically in the form of plug-in modules which provide ready access for servicing and testing. The modules are generally installed in trays which are provided with one or more electrical connectors for mating with the complementary connectors mounted at the modules. In most applications, a plurality of trays are disposed adjacent one another on a common shelf. Frequently, the rack assembly includes two or more shelves positioned vertically with respect to one another.
U.S. Pat. No. 3,771,023 shows a typical tray for receiving a module. The bottom of each tray is provided with a metering plate which permits cooling air to enter the module. An air plenum is disposed below the metering plate for supplying cooling air to each of the trays on the shelf. If the rack assembly has more than one shelf, the plenums for each of the respective shelves are coupled together by a vertical channel sometimes referred to as a "transfer".
In most applications, it is necessary to isolate the electronic modules from shock and vibration. This is especially true of aviation electronic ("avionic") equipment. Heretofore, such isolation was provided for by point-type mechanical isolators disposed at each corner of the unit to be protected. The entire rack assembly can be isolated in this manner, or the individual shelves or trays. It is sometimes preferable to isolate the individual shelves or trays in order to prevent vibration generated by a piece of equipment mounted on one shelf or tray from being transferred to an adjacent shelf or tray.
Point-type isolators are disadvantageous in that they typically require a large amount of space. In avionic applications where space is at a premium, there is frequently not enough clearance to accomodate such isolators. This problem is especially pronounced if the shelves of the rack assembly are to be separately isolated. In addition point-type isolators typically provide for a relatively large amount of displacement of the isolated unit under vibration or shock thereby consuming additional space.
There are prior art mechanical isolators which differ from the previously-described point-type isolators which are used in other applications. Such isolators are disclosed in U.S. Pat. Nos. 3,970,272 and 2,020,092 for motor mounting applications. Although the isolators disclosed in these patents are more compact than the point-type isolators, these patents do not suggest any means for successfully incorporating the isolators in rack assembly for avionic equipment and the like.
The rack assembly disclosed herein overcomes the previously-described shortcomings of the prior art apparatus. The subject assembly provides for mechanical isolation of the individual shelves or trays and is suitable in applications where space is at a premium despite the presence of cooling air plenums. These and other advantages of the disclosed rack assembly will be apparent to one of ordinary skill in the art upon reading the following detailed description of the invention together with the drawings.